The
BOD meter OxiDirect is a device that is designed to determine the
biochemical oxygen demand, called B.O.D. By means of the BOD meter the
samples can be taken without further ado, and the BOD values are
displayed in real-time speed, precisely in mg/l. Each BOD meter
features, depending on the edition, six or twelve sample containers. The
handling of the BOD meter is very comfortable and the measurement period
is selectable for a period of 1 to 28 days. The amount of oxygen
expended for the catabolism of organic substance in water samples is
called the biochemical oxygen demand. By measuring the BOD,
biodegradable substances in water can be determined as well. Therefore
the BOD is an important factor to determine the effect of industrial
waste and that from private household on the water quality in sewage
treatment plants and their receiving waters. The BOD meter OxiDirect
allows an exact and comfortable determination of the BOD, following the
respirometric principle. Therefore the amount of oxygen that is already
metabolized, can be calculated by recording the pressure reduction
inside the sealed BOD meter. Due to the fact that the BOD value of the
sample correlates with its pollution by organic substances, and by that
the value might vary, the BOD meter is customized for the sample volumes
listed below, depending on their measurement range. This results
in a total measurement range of 0 ... 4,000 mg/l. The BOD meter can be
applied on sewage, for determining biological activity rates, on
clarification plants, analytic laboratories, in research and
development.

The
BOD level of a sample depends on its pollution with organic substances
and can be extremely variable. Thus the BOD meter can be configured to
the sample volumes below, depending on the measurement range.

Measurement
range BOD mg/l

Sample
volume ml

0
... 40

428

0
... 80

360

0
... 200

244

0
... 400

157

0
... 800

94

0
... 2000

56

0
... 4000

21.7

Mechanism
of BOD meter OxiDirect

During
the BOD determination the bacteria inside the sample consume the
resolved oxygen. That difference in oxygen of the water compartment is
then replenished by the oxygen from the gas compartment of the sample
container. The resulting carbon dioxide emerging from the metabolism
inside the water compartment and given to the gas compartment enters a
chemical reaction with the potassium hydrate solution inside the tubular
of the BOD meter. By that it is withdrawn from the gas compartment of
the sample container. The ultimate result is a decrease of pressure.
That decrease of pressure is linear proportional to the BOD level and is
measured by the BOD sensor. The BOD value is then immediately displayed
in mg/l.
The recorded BOD values can be displayed in mg/l anytime, without the
need of any additional calculation. Thus e.g. a collection of data over
a weekend can be evaluated in the following week without further ado.
The measurement interval is eligible within 1 to 28 days. BOD
measurements commonly cover a period of 5 days. Short-time measurements
can be useful for the purpose of research. Measurements covering a
period of time are e.g. demanded for OECD determinations.

Thehandling is very simple:Put thetabletintheBOD bottle,start the measurementafter 5 daysread theBBvalue andcompare it with thegiven value.If this value iswithin the tolerance the BODmeasuring system is in order.